In Search of the Wild Bloater

Chubs are a Great Lakes delicacy. The small, deep-water fish is well known for its rich, oily texture. It tends to fly off the shelf, smoked or garnished on the tomato-based “chubby mary.” 

But despite its reputation at the counter, little is known about the silvery fish in parts of its wild habitat. 

“They are very hard to study,” said Max Morgan, captain of the Neeskay, a research vessel at the University of Wisconsin-Milwaukee's School of Freshwater Sciences. “Not a lot of people know a lot about them, except for the fact that they taste really good smoked.”  

The fish is also known as a bloater. It occupies depths between 100 and 600 feet—a hard-to-reach area that isn’t well understood. Native to each Great Lake except Erie, the once-abundant prey fish is extirpated from Lake Ontario, and populations elsewhere are relatively stable but below peak densities of the late 1980s and early 1990s. 

Morgan is part of a research team led by the US Geological Survey (USGS) that is seeking to discover exactly where bloaters spawn in Lake Michigan to test if habitat degradation is impeding a multiagency restoration effort in Lake Ontario. To answer this question, they are braving the notoriously unpredictable winter gales of the Great Lakes to film bloaters in the wild for the first time in never-before-seen parts of the lake. These conditions make the explanation of an already challenging question even more elusive. 

“Working on the water is a lot like working in space. It's very hard,” Morgan said. “Water is a familiar substance, and we generally think it's a friendly substance. But the lakes are cold and brutal if it gets that way.”

"These fish serve a purpose"

Great Lakes fisheries support a $5 billion fishing industry, but human-caused pressures have resulted in unstable populations and immense depletion of biodiversity in the Great Lakes. The fishes with the steepest declines are the coregonine subspecies, which include bloaters: Three species have gone fully extinct, and five have been wiped out from one or more of the five lakes.

In Lake Michigan, for example, commercial catches of the 10-inch fish in Wisconsin waters dropped to 742 pounds in 2019 after consistently harvesting between 1.3 and 2 million pounds per year in the 1980s and 1990s.

Scientists attribute this decline to a combination of degraded water quality, overfishing, and invasive species. Morgan said he wants to make things right. 

“These fish serve a purpose. They are out there for a reason,” he said. “And without things living in the lake, it’s just kind of a cold, dead body of water.”

There’s an ongoing international effort to reintroduce coregonine diversity to the Great Lakes. In 2018, fishery managers from across the US and Canada endorsed a science-based concept called the Coregonine Restoration Framework. Part of the motivation for the initiative is that diversifying native prey fish through bloater restoration helps build resilience to invasive species and climate change, in addition to supporting natural predators like trout and salmon. 

Research biologist Alex Gatch, who is leading the USGS study, said the role of these fish in the region is more than ecological—people depend on a stable fish population.

“What happens when the prey base falls off and that salmon and trout fishery goes away?” he asked. “The folks that are making their money off this, sending their kids to college, paying their mortgage—they are in trouble, right? Part of studying bloater or any of these lower trophic level fishes is that they support that multibillion-dollar fishery.” 

Morgan said some people are born with a connection to the water. 

“When you put me on a boat, I’m in my happy place,” he said. “The connection runs deep, man. It’s a spiritual thing. And these fishermen, when you take that away from them, it’s like taking away their soul.”

One of the grounds for the restoration framework seeking to sustain that connection is in Lake Ontario, where there is an experimental stocking program to rebuild the population. But despite over 2.5 million bloaters stocked since 2012, there isn’t any evidence of natural bloater reproduction. 

That puzzled Gatch, an expert on fish habitat in Lake Ontario. He suspected possibly degraded deep-water ecosystems could be limiting bloater spawning success—but first, he needed to know what healthy bloater spawning habitat looks like in the first place. He called one of the top experts on Lake Michigan bloaters, Bo Bunnell, to find out. But he had to admit, he didn’t know. 

That’s because reaching deep-water spawning grounds miles offshore during the coldest months is a challenging task, said Bunnell, who studies coregonines at USGS. Moreover, scientists don’t have baseline conditions of habitats at these depths before degradation occurred. But the invasion of quagga mussels in deep water changes things. 

“Now I think about spawning habitat as a limitation for all fish should be squarely on the table,” Bunnell said. 

Where’s the bloater?  

The ultimate goal of the study is to discover bloater habitat by filming spawning or capturing eggs. But even with high-tech cameras and ROVs that now enable this type of research, it isn’t necessarily smooth sailing; the team spent weeks looking for bloaters without finding one. 

“We are trying to capture actual spawning on camera, which is incredibly hard to do for any species,” Gatch said. “And we picked the one that spawns during winter in 100 meters of water.”

There are also serious challenges conducting winter research on Lake Michigan. Freezing spray can affect equipment and off-balance the ship. With the right wind direction, ice can quickly jam harbors with impassable sheets that trap boats outside the break walls. Sporadic weather leaves few days with optimal calm conditions. That makes the Neeskay one of the few research vessels in the Great Lakes that goes out in the winter months. 

Once weather conditions align, the search process has been a game of cat and mouse. With scant information about bloater spawning substrates, the team first thought they were lithophilic spawners like similar species and congregate near rocks. After not finding any signs of bloaters at a boulder complex called the Mid-Lake Reef, Morgan called fish markets up the Wisconsin coast hoping to right the ship. He wanted people with the best winter bloater knowledge: commercial fishermen. 

“I told them where we were going, and they were like, ‘Oh yeah no, you’re wrong. You want to get out to the mud.’ They kept stressing the mud,” Morgan said. 

They shifted strategies and moved to clay ridges next to the reef that come out of the relatively flat, silty lakebed, like potholes on a road. Gatch was surprised to find a high level of biodiversity in those micro-habitats—including some egg-eating species. There, the ROV collected a sculpin to be dissected in the lab. They later found a bloater egg in its stomach. 

While the finding is promising, Gatch said it doesn’t necessarily mean bloater spawning occurred there. 

“These egg predators are pretty sedentary, so you can assume where they're eating is close to where you captured them,” he said. “But these eggs are highly mobile, so they could have been released a mile away and currents took them to these habitats.”

To prepare for next season, Gatch will set hundreds of 10-inch-wide egg traps in areas he thinks bloaters spawn to test the new lead and collect them at the source, not just floating around the lakebed or in a predator’s stomach. He’s cautiously optimistic for the results. 

“This is a needle in the haystack. It’s a huge lake and a huge area that we're looking into,” he said. “So any success in catching a single egg I would be happy with, but we'd want to catch hundreds to really confirm that they're spawning somewhere near that site.”

The team has still collected important data despite coming up empty spotting bloaters. For example, they found and filmed lake whitefish deep-water spawning at the Mid-Lake Reef, where there previously wasn't any documentation of it occurring there for that species. Collecting any data in the winter provides important seasonal data when most boats stay at shore. 

But the primary goal remains: Find the “mythical” bloater. 

“Until I've seen one, a real wild bloater, they're just a myth to me,” said Gatch. “We've got a bunch of them in our lab here that are hatchery fish. This doesn't do it for me. I need to see the wild ones.”